The multiple inert gas elimination technique (MIGET) is an established research tool for the determination of ventilation/perfusion (V/Q) distributions in the lung, and the pathophysiologic mechanisms of impaired gas exchange. The MIGET would be tremendously useful for optimizing therapy in the clinical care of patients with pulmonary dysfunction. The traditional approach to MIGET by gas chromatography, however, is laborious and time consuming and as a result has only been used by a handful of research laboratories. This project will apply recent developments in membrane inlet mass spectrometry (MIMS) to the measurements of inert gas tensions in pulmonary arterial and venous blood samples, and mixed expired gas samples. Direct measurement of gas tensions in blood samples by MIMS will eliminate time-consuming gas extraction into a gas phase. Linear dependence of signal on inert gas partial pressure, and independence of signal from variations in inert gas solubility in blood, will be confirmed. The MIMS for MIGET will be automated with computer controlled data acquisition, and computer controlled infusions and sample stream selection. The resulting system for MIGET is expected to analyze blood and gas samples and determine V/Q distributions in less than 20 minutes, and thereby extend an important research tool to the clinical care of patients.